Publications
Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleZbiri M, Gilhooly-Finn PA, Fouquet P, et al., 2022,
Structural Dynamics of Polymer:Non-Fullerene Organic Solar Cell Blends: A Neutron Spectroscopy Perspective
, CHEMISTRY OF MATERIALS, Vol: 34, Pages: 7937-7946, ISSN: 0897-4756 -
Journal articleKafourou P, Qiao Z, Toth M, et al., 2022,
Low Dark Current Organic Photodetectors Utilizing Highly Cyanated Non-fullerene Acceptors
, ACS APPLIED MATERIALS & INTERFACES, ISSN: 1944-8244 -
Journal articleSong J, Zhang M, Hao T, et al., 2022,
Design Rules of the Mixing Phase and Impacts on Device Performance in High-Efficiency Organic Photovoltaics
, RESEARCH, Vol: 2022, ISSN: 2096-5168 -
Journal articleZhao W, Wang J, Tam B, et al., 2022,
Macroporous Vanadium Oxide Ion Storage Films Enable Fast Switching Speed and High Cycling Stability of Electrochromic Devices
, ACS APPLIED MATERIALS & INTERFACES, ISSN: 1944-8244 -
Journal articleCalado P, Gelmetti I, Hilton B, et al., 2022,
Driftfusion: an open source code for simulating ordered semiconductor devices with mixed ionic-electronic conducting materials in one dimension
, JOURNAL OF COMPUTATIONAL ELECTRONICS, Vol: 21, Pages: 960-991, ISSN: 1569-8025- Author Web Link
- Cite
- Citations: 3
-
Journal articleYan J, Rodriguez-Martinez X, Pearce D, et al., 2022,
Identifying structure-absorption relationships and predicting absorption strength of non-fullerene acceptors for organic photovoltaics
, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 15, Pages: 2958-2973, ISSN: 1754-5692- Author Web Link
- Cite
- Citations: 1
-
Journal articleZhu L, Zhang M, Xu J, et al., 2022,
Single-junction organic solar cells with over 19% efficiency enabled by a refined double-fibril network morphology
, NATURE MATERIALS, Vol: 21, Pages: 656-+, ISSN: 1476-1122- Author Web Link
- Cite
- Citations: 127
-
Journal articleHou X, Clarke AJ, Azzouzi M, et al., 2022,
Relationship between molecular properties and degradation mechanisms of organic solar cells based on bis-adducts of phenyl-C-61 butyric acid methyl ester
, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 10, Pages: 7875-7885, ISSN: 2050-7526 -
Journal articleAzzouzi M, Nelson J, Eisner F, et al., 2022,
Reconciling models of interfacial state kinetics and device performance in organic solar cells: Impact of the energy offsets on the power conversion efficiency
, Energy and Environmental Science, Vol: 15, Pages: 156-1270, ISSN: 1754-5692Achieving the simultaneous increases in the open circuit voltage (Voc), short circuit current (Jsc) and fill factor (FF) necessary to further increase the power conversion efficiency (PCE) of organic photovoltaics (OPV) requires a unified understanding of how molecular and device parameters affect all three characteristics. In this contribution, we introduce a framework that for the first time combines different models that have been used separately to describe the different steps of the charge generation and collection processes in OPV devices: a semi-classical rate model for charge recombination processes in OPV devices, zero-dimensional kinetic models for the photogeneration process and exciton dissociation and one-dimensional semiconductor device models. Using this unified multi-scale model in conjunction with experimental techniques (time-resolved absorption spectroscopy, steady-state and transient optoelectronic measurements) that probe the various steps involved in charge generation we can shed light on how the energy offsets in a series of polymer: non-fullerene devices affect the charge carrier generation, collection, and recombination properties of the devices. We find that changing the energy levels of the donor significantly affects not only the transition rates between local-exciton (LE) and charge-transfer (CT) states, but also significantly changes the transition rates between CT and charge-separated (CS) states, challenging the commonly accepted picture of charge generation and recombination. These results show that in order to obtain an accurate picture of charge generation in OPV devices, a variety of different experimental techniques under different conditions in conjunction with a comprehensive model of processes occurring at different time-scales are required.
-
Journal articleKafourou P, Nugraha MI, Nikitaras A, et al., 2021,
Near-IR absorbing molecular semiconductors incorporating cyanated benzothiadiazole acceptors for high performance semi-transparent n-type organic field-effect transistors
, ACS Materials Letters, Vol: 4, Pages: 165-174, ISSN: 2639-4979Small band gap molecular semiconductors are of interest for the development of transparent electronics. Here we report two near-infrared (NIR), n-type small molecule semiconductors, based upon an acceptor-donor-acceptor (A-D-A) approach. We show that the inclusion of molecular spacers between the strong electron accepting end group, 2,1,3-benzothiadiazole-4,5,6-tricarbonitrile, and the donor core affords semiconductors with very low band gaps down to 1 eV. Both materials were synthesised by a one-pot, sixfold nucleophilic displacement of a fluorinated precursor by cyanide. Significant differences in solid-state ordering and charge carrier mobility are observed depending on the nature of the spacer, with a thiophene spacer resulting in solution processed organic field-effect transistors (OFETs) exhibiting excellent electron mobility up to 1.1 cm2 V-1s-1. The use of silver nanowires as the gate electrodes enables the fabrication of semi-transparent OFET device with average visible transmission of 71% in the optical spectrum.
-
Journal articleBozal-Ginesta C, Rao RR, Mesa CA, et al., 2021,
Redox-state kinetics in water-oxidation IrOx electrocatalysts measured by operando spectroelectrochemistry
, ACS Catalysis, Vol: 11, Pages: 15013-15025, ISSN: 2155-5435Hydrous iridium oxides (IrOx) are the best oxygen evolution electrocatalysts available for operation in acidic environments. In this study, we employ time-resolved operando spectroelectrochemistry to investigate the redox-state kinetics of IrOx electrocatalyst films for both water and hydrogen peroxide oxidation. Three different redox species involving Ir3+, Ir3.x+, Ir4+, and Ir4.y+ are identified spectroscopically, and their concentrations are quantified as a function of applied potential. The generation of Ir4.y+ states is found to be the potential-determining step for catalytic water oxidation, while H2O2 oxidation is observed to be driven by the generation of Ir4+ states. The reaction kinetics for water oxidation, determined from the optical signal decays at open circuit, accelerates from ∼20 to <0.5 s with increasing applied potential above 1.3 V versus reversible hydrogen electrode [i.e., turnover frequencies (TOFs) per active Ir state increasing from 0.05 to 2 s–1]. In contrast, the reaction kinetics for H2O2 is found to be almost independent of the applied potential (increasing from 0.1 to 0.3 s–1 over a wider potential window), indicative of a first-order reaction mechanism. These spectroelectrochemical data quantify the increase of both the density of active Ir4.y+ states and the TOFs of these states with applied positive potential, resulting in the observed sharp turn on of catalytic water oxidation current. We reconcile these data with the broader literature while providing a unique kinetic insight into IrOx electrocatalytic reaction mechanisms, indicating a first-order reaction mechanism for H2O2 oxidation driven by Ir4+ states and a higher-order reaction mechanism involving the cooperative interaction of multiple Ir4.y+ states for water oxidation.
-
Journal articleEisner F, Tam B, Belova V, et al., 2021,
Color-tunable hybrid heterojunctions as semi-transparent photovoltaic windows for photoelectrochemical water splitting
, Cell Reports Physical Science, Vol: 2, Pages: 1-16, ISSN: 2666-3864The strong but narrow-bandwidth absorption spectra of organic semiconductors make them excellent candidates for semi-transparent solar cell applications in which color specificity is important. In this study, using a hybrid heterojunction combining the transparent inorganic semiconductor copper thiocyanate (CuSCN) with organic semiconductors (C70, PC70BM, C60, ITIC, IT-4F, or Y6), we show that simple color-tunable solar cells can be fabricated in which the transmission spectrum is determined solely by choice of the organic semiconductor. Using a joint electrical-optical model, we show that it is possible to combine the unique attributes of high photovoltage and color tunability to use these heterojunctions as photovoltaic windows in tandem photoelectrochemical (PEC)-photovoltaic (PV) cells. We demonstrate that this configuration can lead to a reduction in the parasitic absorption losses in the PEC-PV cells and, thus, to solar-to-hydrogen efficiencies (>3%) that are higher than that predicted using the traditionally used architecture in which the PV is placed behind the PEC.
-
ReportPearce D, Pearce A, Gambhir A, et al., 2021,
Research pathways for net-zero transport
The future is uncertain and there are many different pathways ahead for technology and society. Some, but not all, ofthese pathways will deliver the required amount of decarbonisation to comply with the Paris Agreement. Whilst wecannot know for certain which of these pathways will be chosen, research allows us both to identify the patterns andtrends that can help shape the pathways, and ultimately our future, and to develop the technologies and approachesthat can assist decarbonisation
-
Journal articleEisner F, Foot G, Yan J, et al., 2021,
Emissive charge-transfer states at hybrid inorganic/organic heterojunctions enable low non-radiative recombination and high-performance photodetectors
, Advanced Materials, ISSN: 0935-9648Hybrid devices based on a heterojunction between inorganic and organic semiconductors have offered a means to combine the advantages of both classes of materials in optoelectronic devices, but, in practice, the performance of such devices has often been disappointing. Here, it is demonstrated that charge generation in hybrid inorganic–organic heterojunctions consisting of copper thiocyanate (CuSCN) and a variety of molecular acceptors (ITIC, IT-4F, Y6, PC70BM, C70, C60) proceeds via emissive charge-transfer (CT) states analogous to those found at all-organic heterojunctions. Importantly, contrary to what has been observed at previous organic–inorganic heterojunctions, the dissociation of the CT-exciton and subsequent charge separation is efficient, allowing the fabrication of planar photovoltaic devices with very low non-radiative voltage losses (0.21 ± 0.02 V). It is shown that such low non-radiative recombination enables the fabrication of simple and cost-effective near-IR (NIR) detectors with extremely low dark current (4 pA cm−2) and noise spectral density (3 fA Hz−1/2) at no external bias, leading to specific detectivities at NIR wavelengths of just under 1013 Jones, close to the performance of commercial silicon photodetectors. It is believed that this work demonstrates the possibility for hybrid heterojunctions to exploit the unique properties of both inorganic and organic semiconductors for high-performance opto-electronic devices.
-
Journal articleSchmidt J, Weatherby J, Sugden I, et al., 2021,
Computational screening of organic semiconductors: exploring side-group functionalisation and assembly to optimise charge transport in chiral molecules
, Crystal Growth and Design, Vol: 21, Pages: 5036-5049, ISSN: 1528-7483Molecular materials are challenging to design as their packing arrangement and hence properties are subject to subtle variations in the interplay of soft intermolecular interactions that are difficult to predict. The rational design of new molecular materials with tailored properties is currently hampered by the lack of knowledge of how a candidate molecule will pack in space and how we can control the polymorphs we can experimentally obtain. Here, we develop a simplified approach to aid the material design process, by the development of a screening process that is used to test 1344 helicene molecules that have potential as organic electronic materials. Our approach bridges the gap between single molecule design, molecular assembly, and the resulting charge-carrier mobilities. We find that fluorination significantly improves electron transport in the molecular material by up to 200%; the reference [6]helicene packing showed a mobility of 0.30 cm2 V-1 s-1, fluorination increased the mobility to up to 0.96 and 0.97 (13-fluoro[6]H and 4,13-difluoro[6]H), assuming an outer reorganisation energy of 0.30 eV. Side groups containing triple bonds largely lead to improved transfer integrals. We validate our screening approach through the use of crystal structure prediction to confirm the presence of favourable packing motifs to maximize charge mobility.
-
Journal articleSzumska AA, Maria IP, Flagg LQ, et al., 2021,
Reversible Electrochemical Charging of n-Type Conjugated Polymer Electrodes in Aqueous Electrolytes
, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 143, Pages: 14795-14805, ISSN: 0002-7863- Author Web Link
- Cite
- Citations: 17
-
Journal articleDing B, Kim G, Kim Y, et al., 2021,
Influence of backbone curvature on the organic electrochemical transistor performance of glycolated donor–acceptor conjugated polymers
, Angewandte Chemie, Vol: 133, Pages: 19831-19836, ISSN: 0044-8249Two new glycolated semiconducting polymers PgBT(F)2gT and PgBT(F)2gTT of differing backbone curvatures were designed and synthesised for application as p-type accumulation mode organic electrochemical transistor (OECT) materials. Both polymers demonstrated stable and reversible oxidation, accessible within the aqueous electrochemical window, to generate polaronic charge carriers. OECTs fabricated from PgBT(F)2gT featuring a curved backbone geometry attained a higher volumetric capacitance of 170 F cm−3. However, PgBT(F)2gTT with a linear backbone displayed overall superior OECT performance with a normalised peak transconductance of 3.00×104 mS cm−1, owing to its enhanced order, expediting the charge mobility to 0.931 cm2 V−1 s−1.
-
Journal articleJux N, Reger D, Haines P, et al., 2021,
A family of superhelicenes - easily tunable, chiral nanographenes by merging helicity with planar π-systems
, Angewandte Chemie International Edition, Vol: 60, Pages: 18073-18081, ISSN: 1433-7851Incorporating helicity into large polycyclic aromatic hydrocarbons (PAHs) constitutes a new field of research at the interface between chemistry and material sciences. Lately, interest in the design of π-extended helicenes has surged. This new class of twisted, chiral nanographenes not only reveals unique characteristics but also finds its way into emerging applications such as spintronics. Insights into their structure-property relationships and on-demand tuning are scarce. To close these knowledge gaps, we designed a straightforward synthetic route towards a full-fledged family of π-extended helicenes: superhelicenes. Common are two hexa-peri-hexabenzocoronenes (HBCs) connected via a central 5-membered ring. By means of structurally altering this 5-membered ring, we realized a versatile library of molecular building blocks. Not only the superhelicene structure, but also their features are tuned with ease. In-depth physico-chemical characterizations served as a proof of concept thereof. The superhelicene enantiomers were separated, their circular dichroism was measured in preliminary studies and concluded with an enantiomeric assignment. Our work was rounded-off by crystal structure analyses. Mixed stacks of M- and P-isomers led to twisted molecular wires. Using such stacks, charge-carrier mobilities were calculated, giving reason to expect outstanding hole transporting properties.
-
Journal articleReger D, Haines P, Amsharov KY, et al., 2021,
A Family of Superhelicenes: Easily Tunable, Chiral Nanographenes by Merging Helicity with Planar π Systems
, Angewandte Chemie, Vol: 133, Pages: 18221-18229, ISSN: 0044-8249 -
Journal articleDing B, Kim G, Kim Y, et al., 2021,
Influence of backbone curvature on the organic electrochemical transistor performance of glycolated donor-acceptor conjugated polymers
, Angewandte Chemie International Edition, Vol: 60, Pages: 19679-19684, ISSN: 1433-7851Two new glycolated semiconducting polymers PgBT(F)2gT and PgBT(F)2gTT of differing backbone curvatures were designed and synthesised for application as p-type accumulation mode organic electrochemical transistor (OECT) materials. Both polymers demonstrated stable and reversible oxidation, accessible within the aqueous electrochemical window, to generate polaronic charge carriers. OECTs fabricated from PgBT(F)2gT featuring a curved backbone geometry attained a higher volumetric capacitance of 170 F cm−3. However, PgBT(F)2gTT with a linear backbone displayed overall superior OECT performance with a normalised peak transconductance of 3.00×104 mS cm−1, owing to its enhanced order, expediting the charge mobility to 0.931 cm2 V−1 s−1.
-
Journal articleBeath H, Hauser M, Sandwell P, et al., 2021,
The cost and emissions advantages of incorporating anchor loads into solar mini-grids in India
, Renewable and Sustainable Energy Transition, Vol: 1, Pages: 1-14, ISSN: 2667-095XRenewables-based mini-grids have the potential to improve electricity access with lower emissions and better reliability than national grids. However, these systems have a challenging cost to revenue ratio, hindering their implementation. Combining residential loads with an anchor load, a relatively large non-domestic user, can help to improve mini-grid economics. Using measured electricity demand data from India and energy modelling, we assess the cost and emissions advantages of integrating health clinics as anchor loads within domestic solar mini-grids. For comparison, we also assess the ability of the national grid to meet our demand scenarios using monitored grid data. We apply a scenario-based approach, using separate domestic and anchor load demand profiles, and both in combination; we test meeting two levels of energy demand, 95% and 100%; and compare systems using PV and batteries, diesel, and hybrid generation. We find that the national grid has poor availability, at just over 50% at the most comparable monitoring site; and that it would meet a lower fraction of energy demand for our anchor load scenarios than the domestic only ones. For the off-grid systems, we find substantial cost and emissions reductions with anchor loads relative to demand scenarios without anchor loads. At 95% of demand met, we find PV and battery systems are 14-22% cheaper than diesel-only systems, with 10 times lower carbon intensity. Our findings illustrate the role off-grid systems can play in the provision of reliable low-carbon electricity and highlight the advantages of incorporating anchor loads like health centres into such systems.
-
Journal articleZbiri M, Finn PA, Nielsen CB, et al., 2021,
Quantitative insights into the phase behaviour and miscibility of organic photovoltaic active layers from the perspective of neutron spectroscopy
, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 9, Pages: 11873-11881, ISSN: 2050-7526- Author Web Link
- Cite
- Citations: 2
-
Journal articleEisner F, Nelson J, 2021,
Barrierless charge generation at non-fullerene organic heterojunctions comes at a cost
, Joule, Vol: 5, Pages: 1319-1322, ISSN: 2542-4351The advent of non-fullerene acceptors has enabled organic solar cells to reach power conversion efficiencies that were previously thought unreachable. However, in a recent Nature Materials article, Karuthedath and colleagues show that the electrostatic environment at the interface might put a limit to how much further they can be improved.
-
Journal articleYan J, Rezasoltani E, Azzouzi M, et al., 2021,
Influence of static disorder of charge transfer state on voltage loss in organic photovoltaics
, Nature Communications, Vol: 12, ISSN: 2041-1723Spectroscopic measurements of charge transfer (CT) states provide valuable insight into the voltage losses in organic photovoltaics (OPVs). Correct interpretation of CT-state spectra depends on knowledge of the underlying broadening mechanisms, and the relative importance of molecular vibrational broadening and variations in the CT-state energy (static disorder). Here, we present a physical model, that obeys the principle of detailed balance between photon absorption and emission, of the impact of CT-state static disorder on voltage losses in OPVs. We demonstrate that neglect of CT-state disorder in the analysis of spectra may lead to incorrect estimation of voltage losses in OPV devices. We show, using measurements of polymer:non-fullerene blends of different composition, how our model can be used to infer variations in CT-state energy distribution that result from variations in film microstructure. This work highlights the potential impact of static disorder on the characteristics of disordered organic blend devices.
-
Journal articleZhang M, Guo F, Zhou Q, et al., 2021,
Enhanced performance through trap states passivation in quantum dot light emitting diode
, Journal of Luminescence, Vol: 234, Pages: 1-7, ISSN: 0022-2313Device performance enhancement in quantum dot light-emitting diodes (QLEDs) is realized by adding a small amount of insulating polymer polymethyl methacrylate (PMMA) into the emitting quantum dot layer. Pool-Frenkel effect is observed through temperature-dependent current density-voltage experiments, indicating the important role of trap states, and the addition of the insulating PMMA helps to reduce the Poole-Frenkel barrier hence the trap depth. Reduced density and depth of trap states with PMMA are indeed observed through further capacitance measurements. This work contributes to a better understanding on the effects of traps in QLEDs.
-
Journal articleOrtega-Arriaga P, Babacan O, Nelson J, et al., 2021,
Grid versus off-grid electricity access options: A review on the economic and environmental impacts
, Renewable and Sustainable Energy Reviews, Vol: 143, Pages: 1-17, ISSN: 1364-0321This research reviews the economic and environmental impacts of grid-extension and off-grid systems, to inform the appropriate electrification strategy for the current population without electricity access. The principal technologies reviewed are centralised conventional fossil-fuel grid-extension and off-grid systems mainly based on solar PV and batteries. It finds that relatively few studies explicitly compare grid-extension electricity costs against off-grid systems costs and that there is a lack of consistency in the methodologies used to determine the least-cost solution. Nevertheless, the studies reviewed show a range of around $0.2–1.4/kWh for off-grid electricity access, compared to a range of below $0.1/kWh to more than $8/kWh for grid access, pointing to a number of cases in which off-grid access may already be the more cost-effective option. Existing literature on the environmental impacts primarily focuses on greenhouse gas emissions from electricity generation, with off-grid (solar PV and storage) systems’ emissions in the range of 50–130 gCO2-eq/kWh and grid generation from close to 0 gCO2-eq/kWh (for renewables and nuclear sources) to over 1,000 gCO2-eq/kWh (for coal). Emissions impacts stemming from transmission and distribution grids suggest a range of 0–30 gCO2-eq/kWh. Assessments of other environmental impacts such as water use, land use, biodiversity and e-waste are often absent in studies, whilst few studies explicitly compare the environmental impacts of grid versus off-grid systems. Further research should focus on comparing the costs of electricity access options using consistent metrics, expanding the scope of environmental impacts analysis, and integrating environmental and economic impacts into a comprehensive sustainability assessment of different options.
-
Journal articleCilio L, Babacan O, 2021,
Allocation optimisation of rapid charging stations in large urban areas to support fully electric taxi fleets
, APPLIED ENERGY, Vol: 295, ISSN: 0306-2619- Author Web Link
- Cite
- Citations: 7
-
Journal articleMoss B, Babacan O, Kafizas A, et al., 2021,
A review of inorganic photoelectrode developments and reactor scale-up challenges for solar hydrogen production
, Advanced Energy Materials, Vol: 11, Pages: 1-43, ISSN: 1614-6832Green hydrogen, produced using solar energy, is a promising means of reducing greenhouse gas emissions. Photoelectrochemical (PEC) water splitting devices can produce hydrogen using sunlight and integrate the distinct functions of photovoltaics and electrolyzers in a single device. There is flexibility in the degree of integration between these electrical and chemical energy generating components, and so a plethora of archetypal PEC device designs has emerged. Although some materials have effectively been ruled out for use in commercial PEC devices, many principles of material design and synthesis have been learned. Here, the fundamental requirements of PEC materials, the top performances of the most widely studied inorganic photoelectrode materials, and reactor structures reported for unassisted solar water splitting are revisited. The main phenomena limiting the performance of up‐scaled PEC devices are discussed, showing that engineering must be considered in parallel with material development for the future piloting of PEC water splitting systems. To establish the future commercial viability of this technology, more accurate techno‐economic analyses should be carried out using data from larger scale demonstrations, and hence more durable and efficient PEC systems need to be developed that meet the challenges imposed from both material and engineering perspectives.
-
Journal articleBaranda Alonso J, Sandwell P, Nelson J, 2021,
The potential for solar-diesel hybrid mini-grids in refugee camps: A case study of Nyabiheke camp, Rwanda
, Sustainable Energy Technologies and Assessments, Vol: 44, Pages: 1-18, ISSN: 2213-1388Electricity access in refugee camps is often limited to critical operations for humanitarian agencies and typically powered by diesel generators. We study the economic and environmental benefits that optimised fully renewable and diesel-hybrid mini-grid designs can provide in humanitarian settings by displacing diesel use. Considering the case study of Nyabiheke camp in Rwanda we found that these benefits are substantial, with total cost and emissions reductions of up to 32% and 83% respectively, and cost payback times ranging from 0.9 to 6.2 years. Despite their different cost structures, we find that all levels of hybridisation provide cost and emission savings compared to the incumbent diesel system, with hybrid systems being able to offset emissions more cost-effectively than fully renewable systems. We highlight how modelling tools can facilitate the introduction and progressive expansion of systems, improving asset utilisation and reducing lifetime costs compared to one-off installations, and can inform operational considerations on the ground. These benefits are enhanced when connecting productive users for whom demand matches the solar generation profile. Multiple energy needs and objectives can be met simultaneously but financial resources, environmental considerations and operational timeframes will influence the most appropriate system design for humanitarian actors on a case-by-case basis.
-
Journal articleGuilbert AAY, Parr ZS, Kreouzis T, et al., 2021,
Effect of substituting non-polar chains with polar chains on the structural dynamics of small organic molecule and polymer semiconductors
, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 7462-7471, ISSN: 1463-9076- Author Web Link
- Cite
- Citations: 3
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.